Synthesis and Electrochemistry of Acicular Silver Vanadium Oxide Nanofibers
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0972-AA06-06
Synthesis and Electrochemistry of Acicular Silver Vanadium Oxide Nanofibers Kenneth J. Takeuchi1, Amy C. Marschilok2, Randolph A. Leising2, and Esther S. Takeuchi2 1 Department of Chemistry, University at Buffalo, Buffalo, NY, 14260 2 Research and Development, Greatbatch, Inc., Clarence, NY, 14031
ABSTRACT Silver vanadium oxide (SVO, Ag2V4O11) has demonstrated commercial success as a solid-state cathode material in power sources for implantable biomedical devices. This report describes the synthesis of SVO via a hydrothermal method. This novel synthetic approach allows low temperature production of acicular SVO nanofibers with a high surface area. This material was investigated as a cathode material in primary lithium batteries for high rate pulse applications.
INTRODUCTION Silver vanadium oxide / lithium batteries are the commercial standard for powering implantable cardiac defibrillators, due to their high volumetric energy density and their ability to deliver rapid high energy pulses. The structure of silver vanadium oxide (SVO, Ag2V4O11) makes it suited to this demanding application, as it provides accessible pathways for rapid diffusion of lithium ions. The history behind the synthetic development of silver vanadium oxide has been extensively reviewed.[1] Traditionally, solid-state chemical decomposition,[2,3] combination,[4] and decomposition/combination reactions [5] have been utilized to prepare SVO. More recently, new strategies have been utilized for SVO synthesis, including sol-gel methods,[6] rhelogical phase methods,[7] and microwave assisted syntheses [8]. Zhu and coworkers recently reported hydrothermal synthesis and magnetic properties of Ag2V4O11 nanobelts [9]. A mixture of V2O5, AgNO3 and 1,6-hexanediamine was heated in water to form nanobelts with diameters on the order of 70-200 nm, and lengths of 2-5 µm. In this work, a stoichiometric mixture of Ag2O and V2O5 has been utilized to generate nanosized acicular Ag2V4O11 with a high surface area, in the absence of any organic template or other additives. The hydrothermal SVO product formed was pure ε-phase SVO. Electrochemical studies were undertaken to investigate the possible utility of the hydrothermally produced SVO as a cathode for primary lithium batteries under high pulse rate applications.
EXPERIMENTAL DETAILS A 1:2 molar ratio of Ag2O and V2O5 was combined with water in an acid digestion bomb and heated for 36 hours at approximately 200oC to produce hydrothermal SVO. For comparison, SVO was also synthesized on a lab scale by the chemical decomposition method [3]. X-ray powder diffraction (XRD), scanning electron microscopy (SEM), and Brunauer, Emmett, and Teller (BET) surface area measurements were used to characterize the SVO materials. XRD data were collected with a Shimadzu Lab X-6000 x-ray diffractometer using fixed divergence and scatter slits of 1.00 mm, a receiving slit of 0.30 mm, and Cu Kα radiation. A Micromeritics Gemini 5 automatic volume sorption analyzer was used for BET surface area analysis, using N2 as an a
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